In this photo taken on Sunday, Dec. 1, 2013, Metro North Railroad engineer William Rockefeller is wheeled on a stretcher away from the area where the commuter train he was operating derailed in the Bronx borough of New York. The National Transportation Safety Board reported Monday that the train Rockefeller was driving was going 82 mph around a 30-mph curve when it derailed killing four people and injuring more than 60. (AP Photo/Robert Stolarik)

A train passes by the scene of repair efforts at the site of a train derailment in the Bronx borough of New York, Tuesday, Dec. 3, 2013. The National Transportation Safety Board says right now, it doesn't know whether faulty brakes or human error caused Sunday's derailment of a New York City train that killed four people and injured more than 60. But NTSB member Earl Weener says information from the train's two data recorders shows the train was going 82 mph on a turn when it should have been going no more than 30 mph. (AP Photo/Seth Wenig)

NEW YORK (AP) — He's worked on the railroad for two decades, but engineer William Rockefeller's life may be defined by what he did in the seconds before his speeding commuter train flew off the tracks along a sharp bend.

While investigators have yet to finish talking with him, a darkening cloud of questions is forming around Rockefeller because the Metro-North Railroad train went into the curve at 82 mph, or nearly three times the speed limit. Four people were killed and dozens injured.

As National Transportation Safety Board continued working Tuesday to determine what caused the Sunday morning wreck in the Bronx, Gov. Andrew Cuomo said Rockefeller should be disciplined for "unjustifiable" speed.

Rockefeller stayed out of sight.

"This is a man who is totally distraught by the loss of life, and he's having a tough time dealing with that," said Anthony Bottalico, his union leader.

NTSB member Earl Weener said Monday that information from the data recorders indicates the throttle was let up and the brakes were fully applied just five or six seconds before the train came to a grinding, smoking halt.

Investigators said it was soon to say whether the excessive speed was the result of human error — say, a sleepy or distracted operator — or a mechanical problem.

But Weener said investigators hadn't found any evidence of brake trouble during the train's nine previous stops.

Investigators began talking to the engineer Monday but didn't complete the interview. It is unlikely to resume until Wednesday, NTSB spokesman Keith Holloway said Tuesday.

He said he had no information on why; Bottalico said the session wasn't finished because Rockefeller was distressed and hadn't slept in almost 24 hours.

Rockefeller was given drug and alcohol tests — the results weren't available Monday, Weener said — and investigators were examining the engineer's cellphone. Engineers can have cellphones but are not allowed to use them during a train's run.

The New York Police Department is conducting its own investigation, with help from the Bronx district attorney's office, in the event the derailment becomes a criminal case.

Whatever the findings on the cause of the crash, Cuomo said Tuesday the engineer could be faulted for the train's speed alone.

"Certainly, we want to make sure that that operator is disciplined in an appropriate way. There's such a gross deviation from the norm," he said.

An attorney for Rockefeller didn't immediately return calls Tuesday, but his union spoke up in his defense.

"Once the NTSB is done with their investigation and Billy is finished with his interview, it will be quite evident that there was no criminal intent with the operation of his train," Bottalico said.

Rockefeller, 46 and married with no children, has worked for the railroad for about 20 years and has been an engineer for 11, Bottalico said. Rockefeller lives in a well-kept house on a modest rural road in Germantown, N.Y., about 40 miles south of Albany.

He started as a custodian at Grand Central Terminal, then monitored the building's fire alarms and other systems, and ultimately became an engineer.

"He was a stellar employee. Unbelievable," said his former supervisor, Michael McLendon, who retired from the railroad about a year ago.

McLendon said he was stunned when he heard about the crash, shortly after opening his mail to find a Christmas card from Rockefeller and his wife.

"I said, 'Well, I can't imagine Billy making a mistake,'" McLendon said. "Not intentionally, by any stretch of the imagination."

Rockefeller's work routine had recently changed. He had begun running that route on Nov. 17, two weeks before the wreck, said Marjorie Anders, a spokeswoman for Metro-North's parent, the Metropolitan Transportation Authority.

Bottalico said Rockefeller had changed work schedules — switching from afternoons to the day shift, which typically begins at 5 a.m. — but was familiar with the route and qualified to run it.

In case of an engineer becoming incapacitated, the train's front car was equipped with a "dead man's pedal" that must be depressed or else the train will automatically slow down, Anders said.

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